1. Field of the Invention
This invention relates to a method for making a frame-like shell which is to be fixed around a refractory body for reinforcing purposes.
2. Description of Related Art
A refractory has good fire resistance, poor strength and brittleness. A frame-like shell is often used to reinforce the refractory body.
For example, a sliding plate for opening or closing a gate in a continuous steel casting apparatus includes a body made of a refractory material and a frame-like shell made of a metal. The body is fixed within the frame-like shell by a well-known shrinkage fit method.
FIG. 7 shows a conventional frame-like shell 21 into which a sliding plate refractory body is fitted. In order to make the frame-like shell 21, a pair of U-shaped bent members 22 are joined to each other at their opposite ends 23 by two welds 24. When the bent members 22 are formed in a U-shape by a press apparatus, buckling or spring back is apt to take place. Thus, it is difficult to precisely shape the bent members 22. The opposite ends 23 of the bent members 22 are apt to be dislocated when they are joined. If such bent members 22 are joined by the welds 24, they deform.